“I dropped out of school myself, and I promised my dad I’d go back,” Bill Gates told a theater filled with Berkeley students on Monday. Fittingly, perhaps, the Microsoft magnate-turned-philanthropist — whose transportation to campus involved a helicopter landing at Edwards Field — seemed keener to pose questions than to impart wisdom.

“Are the brightest minds working on the most important problems?” wondered Gates, who became a leader of the personal-computer revolution — and one of the world’s wealthiest people — without benefit of a college degree. How, he wanted to know, “do we draw more people in” to address global poverty and its attendant miseries, including hunger, disease and lack of access to education?

“Is it the visibility, that they don’t see those challenges, that they don’t have the awareness? Do they not know the success stories?” he asked. “I don’t have the answer to this. But it is something that I challenge you to think about.”

Bill Gates, in Cal cap, talks with Gates Scholars.

Taking the Zellerbach Hall stage for the first leg of a five-university “College Tour Challenge” — his next stop was Stanford, with visits to the University of Chicago, Harvard and MIT to follow — Gates said this was his first appearance before a college audience in two years. That’s how long he’s been devoting himself full-time to what has become the world’s largest philanthropy, his own Bill & Melinda Gates Foundation.

What Gates sees as the world’s “most important problems” are, not surprisingly, those he has made the focus of the foundation’s work, and particularly those associated with “inequities in poor countries,” including food production, health and education. “We want to take all the excitement and energy possible and apply them to these things,” he said.

But Gates, relaxed and roaming the front of the stage in an open-necked pinstriped shirt equipped with a clip-on microphone, lamented the size of the talent pool for endeavors like sports and “baldness cures,” for example, in contrast to the “tiny” number of this country’s “brightest minds” working on global-poverty and health issues.

At the top of his 20-minute talk — after which he shared the stage for another half-hour with Executive Vice Chancellor and Provost George Breslauer while answering questions submitted by audience members — Gates recalled a recent session of “goofing off” with friends whose expertise and intensity were most noticeable in two areas: “March madness” and Wall Street.

“Could we be having that same conversation about seeds that would make poor farmers more productive?” he asked himself. “And I thought, maybe not. We’re going to have to work on this.”

Gates pointed to some positive developments in the world, including a steady, 50-year decline in the mortality rate for children under the age of 5. He attributed the improvement — from more than 20 million deaths a year in 1960 to fewer than 8 million today — to “the invention and delivery of a small number of vaccines,” crediting the measles vaccine and the elimination of smallpox alone with saving roughly 2 million children under 5 every year.

Even concerns that improving life expectancy in impoverished areas means increasing population growth in those areas — leaving still more people uneducated, unfed and unemployed, and potentially exacerbating environmental damage due to higher density — have proved largely unfounded, he said.

“The phenomenal thing we learned is that as you improve health in a society, very rapidly the birthrate drops,” he said, attributing the change to parents’ desire to have fewer, but healthier, children.

Gates also drew a direct line from increased educational levels to economic success, but worried that even in the United States, higher tuition is putting college “a bit out of reach” for many. “The University of California,” he added, “is Exhibit A.”

One student’s question struck a particularly responsive chord from the near-capacity audience. “As a graduating senior with no job and ever-mounting financial concerns,” it read, “how can I still make a difference in the topics you spoke of today?”

“Well,” replied Gates, “you’re probably not going to be too picky about a gigantic salary, so that’s good.” Observing that this is “a tough time to graduate,” he said that students might view the grim job market as “a time in your life when you could take a year or two to work in an underdeveloped country,” and turn the situation “into a positive.”

And he applauded Berkeley students for their demonstrated interest in such groups as Teach for America, which recruits college graduates to teach in low-income schools. That, he suggested, is a step toward changing an American mindset that makes it easier to find talented people to promote new software products than to help save lives.

Such a change in priorities, he said, “might delay the next baldness cure. It might delay the next fancy derivative financial product. But if it helps solve some of the big problems, I think that’s a good thing.”

Besides his Zellerbach appearance, Gates’ visit to Berkeley included breakfast with faculty members at University House, a tour of Professor Daniel Portnoy’s lab — which focuses on the microbiology and immunology of infections caused by intracellular pathogens — and a meeting with some of the campus’s Gates Millennium Scholars.